Over the years various kinds of machines have been developed for cleaning and maintaining floors inside buildings, and paved outdoor areas such as streets, sidewalks and parking lots. They include such machines as rotary broom sweepers, vacuum sweepers, scarifiers, burnishers, polishers and scrubbers. For our purposes here they can be divided into machines which apply water to the surface being maintained and machines which operate dry. We are concerned with the latter, which would include many vacuum sweepers, scarifiers, and rotary broom sweepers. They all share one problem which is addressed by this invention. In their normal operation they tend to stir up dust from the surface being maintained. If it is not controlled, this dust is highly objectionable.
On many of these machines the problem has received one general solution. The functional tool which generates the dust, such as a rotary broom, a scarifier head, or a vacuum pickup, is provided with a cover and surrounded by walls which have rubber skirts that hang down almost to the surface being maintained. An on board exhaust blower continuously pulls air from the tool chamber thus created so there is a sub-atmospheric air pressure within it which eliminates outflow of dusty air from under the skirts. The blower exhausts this air to atmosphere. One or more air filters are placed in this air path, either upstream or downstream from the blower, to remove dust from the air before it is released so the discharge to atmosphere will be dust free.
An aspect of the present invention is to provide a cyclone dust-collector within a debris hopper of a surface cleaning machine having an improved construction which is capable of separating and collecting the fine particles efficiently.
The above aspect is achieved by providing a cyclonic prefilter which filters out dust and dirt from drawn-in air. In one example, the cyclonic prefilter includes multiple cyclone units for centrifugally separating the dust and dirt from the drawn-in air, and a cover unit defined as the upper housing of the cyclonic prefilter, for allowing the cyclone-filtered air to fluidly communicate with an air inlet of a filter box for subsequent filtering.
The cyclone units may comprise an air guide wall for inducing rotational flow to the air stream. A plurality of the funnel-shaped members may be arranged in a predetermined pattern, forming a multiple cyclone unit. The top housing may comprise a first cover connected to the upper portion of the multiple cyclone unit, and having centrifugal passages for guiding the air discharged from the cyclones to be a vortex, and discharge holes through which air exiting from the discharge holes is drawn.